IVL Swedish Environmental Research Institute

With great joy and pride, we present this anniversary publication to celebrate 40 years of environmental monitoring within SWETHRO – the Swedish Throughfall Monitoring Network. Over the past four decades, SWETHRO – operated by IVL Swedish Environmental Research Institute in collaboration with Lund University – has played a key role in Sweden’s regional and national forest environmental monitoring. The monitoring network maps atmospheric deposition of air pollutants and evaluates the effects on forest soils. At our previous 30th anniversary, we highlighted how SWETHRO had documented the substantial reduction in sulphur deposition across Sweden – an environmental policy success. At the same time, ongoing challenges were identified, particularly related to nitrogen deposition and the slow recovery of forest soils from acidification.

Ten years later, these issues remain relevant, while at the same time new questions and perspectives have emerged. SWETHRO has continued to evolve, strengthening collaborations with regional air quality protection associations, researchers, authorities, and international partners to provide a more detailed understanding of how air pollution affects Swedish forest ecosystems. Its strong connection to research ensures that the monitoring data are analyzed and interpreted as accurately as possible, thereby reinforcing both environmental monitoring and the scientific basis for future decision-making. This anniversary publication summarizes key findings and insights from four decades of environmental monitoring within SWETHRO and showcases the strengths that can help meet the environmental challenges of tomorrow. We hope it will inspire continued engagement in protecting and preserving our forests for future generations.